Methods and systems for controlling steering systems of vehicles

ABSTRACT

Methods and systems are provided for controlling a steering system of a vehicle is provided. A detection unit is configured to obtain one or more of the following values: a compass heading, a global positioning system (GPS) heading, a yaw velocity, and a difference in tire angular velocities. A processor is coupled to the detection unit, and is configured to determine whether a vehicle is on a straight line path using one or more of the compass heading, the GPS heading, the yaw velocity, and the difference in tire angular velocities, activate the steering system if it is determined that the vehicle is on a straight line path, and disable the feature of the steering system if it is determined that the vehicle is not on a straight line path.

TECHNICAL FIELD

The present disclosure generally relates to vehicles, and moreparticularly relates to methods and systems for controlling steeringsystems of vehicles.

BACKGROUND

Certain vehicles today have EPS (Electric Power Steering) systems thatprovide torque compensation when either short term or long termconditions may otherwise result in an off-center pull of the steeringwheel. Such torque compensation for steering may be desirable insituations in which the vehicle regularly leads or pulls in a directionthat is not intended by the driver (a lead/pull condition), and whichwould require the driver to apply torque to the steering wheel even ifthe vehicle was travelling along a straight line path on a smooth, flat,and non-inclined road.

Torque-reducing EPS steering systems of vehicles may not always provideoptimal torque compensation, for example in distinguishing betweenstraight-line driving as compared with operation on a relativelylong-radius turn (such as a freeway ramp).

Accordingly, it is desirable to provide an improved method forcontrolling steering systems of vehicles, for example, by employingimproved discrimination between straight-line driving as compared withoperation on a relatively long-radius turn (such as a freeway ramp). Itis also desirable to provide an improved system for controlling steeringsystems, as well as to provide improved vehicles that include suchmethods and/or systems. Furthermore, other desirable features andcharacteristics of the present invention will become apparent from thesubsequent detailed description of the invention and the appendedclaims, taken in conjunction with the accompanying drawings and thisbackground of the invention.

SUMMARY

In accordance with an exemplary embodiment, a method of controlling asteering system of a vehicle is provided. The method comprisesdetermining whether the vehicle is on a straight line path based on oneor more of the following values: a compass heading, a global positioningsystem (GPS) heading, a yaw velocity, and a difference in tire angularvelocities, activating a feature of the steering system if it isdetermined that the vehicle is on a straight line path, and disablingthe feature of the steering system if it is determined that the vehicleis not on a straight line path.

In accordance with another exemplary embodiment, a system forcontrolling a steering system of a vehicle is provided. The systemcomprises a detection unit and a processor. The detection unit isconfigured to obtain one or more of the following values: a compassheading, a global positioning system (GPS) heading, a yaw velocity,and/or a tire angular velocity difference. The processor is coupled tothe detection unit, and is configured to determine whether a vehicle ison a straight line path using one or more of the compass heading, theGPS heading, the yaw velocity, and/or the tire angular velocitydifference, activate a feature of the steering system if it isdetermined that the vehicle is on a straight line path, and disable thefeature of the steering system if it is determined that the vehicle isnot on a straight line path.

In accordance with a further exemplary embodiment, a vehicle isprovided. The vehicle comprises a drive system, and electric powersteering system, and a control system. The electric power steeringsystem is coupled to the drive system. The control system is coupled tothe electric power system. The control system comprises a detection unitand a processor. The detection unit is configured to obtain one or moreof the following values: a compass heading, a global positioning system(GPS) heading, a yaw velocity, and/or a tire angular velocitydifference. The processor is coupled to the detection unit andconfigured to determine whether a vehicle is on a straight line pathusing one or more of the compass heading, the GPS heading, the yawvelocity, and/or the tire angular velocity difference, activate alead/pull compensation feature of the steering system if it isdetermined that the vehicle is on a straight line path, and terminatethe lead/pull compensation or maintain a level of torque based onprevious learning, if it is determined that the vehicle is not on astraight line path.

DESCRIPTION OF THE DRAWINGS

The present disclosure will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and:

FIG. 1 is a functional block diagram of a vehicle that includes, amongother features, an electric power steering system, and a control systemfor controlling the electric power steering system, in accordance withan exemplary embodiment;

FIG. 2 is a functional block diagram of the electric power steeringsystem and the control system of FIG. 1, in accordance with an exemplaryembodiment; and

FIG. 3 is a flowchart of a process for controlling a steering system,and that can be used in conjunction with the vehicle of FIG. 1 and theElectric Power Steering and the control system of FIG. 2, in accordancewith an exemplary embodiment.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the disclosure or the application and usesthereof. Furthermore, there is no intention to be bound by any theorypresented in the preceding background or the following detaileddescription.

FIG. 1 illustrates a vehicle 100, or automobile, according to anexemplary embodiment. The vehicle 100 is also referenced at variouspoints throughout this Application as the host vehicle. As described ingreater detail further below, the vehicle 100 includes an electric powersteering system (EPS) (also referred to herein as a steering system) anda control system that controls the steering functionality using, amongother factors, discrimination between straight-line driving and vehicleturns, including vehicle turns with relatively long radii (such as afreeway ramp).

As depicted in FIG. 1, the vehicle 100 includes a chassis 112, a body114, four wheels 116, an electronic control system 118, a steeringsystem 150, a braking system 160, and a control system 170. The body 114is arranged on the chassis 112 and substantially encloses the othercomponents of the vehicle 100. The body 114 and the chassis 112 mayjointly form a frame. The wheels 116 are each rotationally coupled tothe chassis 112 near a respective corner of the body 114.

The vehicle 100 may be any one of a number of different types ofautomobiles, such as, for example, a sedan, a wagon, a truck, or a sportutility vehicle (SUV), and may be two-wheel drive (2WD) (i.e.,rear-wheel drive or front-wheel drive), four-wheel drive (4WD) orall-wheel drive (AWD). The vehicle 100 may also incorporate any one of,or combination of, a number of different types of propulsion systems,such as, for example, a gasoline or diesel fueled combustion engine, a“flex fuel vehicle” (FFV) engine (i.e., using a mixture of gasoline andethanol), a gaseous compound (e.g., hydrogen or natural gas) fueledengine, a combustion/electric motor hybrid engine, and an electricmotor.

In the exemplary embodiment illustrated in FIG. 1, the vehicle 100 hasan internal combustion engine 130, and includes an actuator assembly120. The actuator assembly 120 includes at least one propulsion system129 mounted on the chassis 112 that drives the wheels 116. Thepropulsion system 129 comprises a drive system that propels the vehicle100. In the depicted embodiment, the actuator assembly 120 includes aninternal combustion engine 130. Still referring to FIG. 1, thecombustion engine 130 is integrated such that the engine 130 ismechanically coupled to at least some of the wheels 116 through one ormore drive shafts 134. As depicted in FIG. 1, the vehicle 100 may alsoinclude a radiator 128 for cooling the engine 130.

The steering system 150 is mounted on the chassis 112 or body 114, andcontrols steering of the wheels 116. The steering system 150 iscomprised of an Electric Power Steering (EPS) module. A more detaileddepiction of the steering system 150 is provided in FIG. 2 and discussedfurther below in connection therewith, in accordance with an exemplaryembodiment.

The braking system 160 is mounted on the chassis 112, and providesbraking for the vehicle 100. The braking system 160 receives inputs fromthe driver via a brake pedal (not depicted), and provides appropriatebraking via brake units (also not depicted). In addition, as mentionedbelow, in certain embodiments steering compensation is disabled ormodified when the braking system 160 is engaged by the driver of thevehicle 100.

The control system 170 is coupled to the steering system 150, andcontrols operation thereof. The control system 170 may also be coupledto various other vehicle devices and systems, such as, among others, theactuator assembly 120, the braking system 160, and the electroniccontrol system 118. A more detailed depiction of the control system 170is provided in FIG. 2 and discussed further below in connectiontherewith, in accordance with an exemplary embodiment.

FIG. 2 is a schematic drawing of a system 200 for providing andcontrolling functionality for an Electric Power Steering (EPS) systemfor a vehicle, such as the vehicle 100 of FIG. 1, in accordance with anexemplary embodiment. As depicted in FIG. 2, the system 200 includes thesteering system 150 of FIG. 1 and the control system 170 of FIG. 1, inaccordance with an exemplary embodiment. The system 200 provides forcontrol of the steering functionality using, among other factors,differentiation between straight-line driving and vehicle turns,including vehicle turns with relatively long radii (such as a freewayramp). The system 200 preferably performs such functions using the stepsof the process 300 depicted in FIG. 3 and described further below inconnection therewith.

The vehicle steering system 150 includes a steering wheel 212, asteering column assembly 214, a rack 216 having a rack housing 217, acontrol pinion 218, an electric motor 219, an assist pinion 220, one ormore tie rods 222, and an intermediate shaft 213. The steering columnassembly 214 is coupled to the steering wheel 212, and is rotationallymovable thereby. The steering column assembly 214 is configured to atleast facilitate movement of wheels of the vehicle based at least inpart on movement of the steering wheel 212. Specifically, operation ofthe steering wheel 212 causes rotational movement of the steering columnassembly 214 and intermediate shaft 213, which in turn causestranslational movement of the rack 216 and tie rods 222 via the controlpinion 218 and the assist pinion 220, and thereby ultimately causingrotation of the wheels of the vehicle. While the embodiment of thevehicle steering system 150 of FIG. 1 comprises a dual pinion (DP)electrically powered steering system, in certain other embodiments othertypes of steering systems may be used, such as a column type electricpower steering system (CEPS) or a belt drive (BD) electrically poweredsteering system.

The control system 170 is coupled to the steering system 150, andcontrols operation thereof. The control system 170 (preferably, theprocessor 270 thereof, described further below) provides instructions tothe motor 219 to provide, under appropriate conditions, compensatingtorque against the rack 216 (to thereby balance any unwanted torquecaused by environmental conditions such as wind gusts or crowns in theroadway, or by vehicle conditions such as a vehicle alignment and tireeffects). In certain embodiments, the motor 219 may provide compensatingtorque against the steering column assembly 214 and/or the steeringwheel 212.

The control system 170 provides for control of the steeringfunctionality of the steering system 150 using, among other factors,differentiation between straight-line driving and vehicle turns,including vehicle turns with relatively long radii (such as a freewayramp). The control system 170 preferably performs such functions usingthe steps of the process 300 depicted in FIG. 3 and described furtherbelow in connection therewith.

As depicted in FIG. 2, the control system 170 uses signals from at leastone of a compass 250, a global positioning system (GPS) device 252, asensor array 254, and a controller 256. The compass 250 measures valuesas to a heading of the vehicle at various points in time and providessuch compass heading values for the controller 256 for processing. TheGPS device 252 receives values as to a heading of the vehicle(preferably using a non-depicted GPS satellite system) and provides suchGPS heading values for the controller 256 for processing.

The sensor array 254 is coupled to the controller 256. The sensor array254 includes one or more torque sensors 260, yaw rate sensors 262, andwheel sensors 266.

The torque sensor 260 measures a torque applied by a driver of thevehicle to the steering wheel 212 and/or the steering column assembly214. In one embodiment, the torque sensor 260 is coupled to the steeringwheel 212, and measures a torque applied by the driver against thesteering wheel 212. In another embodiment, the torque sensor 260 iscoupled to the steering column assembly 214, and measures a torqueapplied to the steering torque assembly 214 resulting from the driver'sapplication of the steering wheel 212. It is noted that, in certainembodiments, the torque sensor 260 can be disposed in the steeringcolumn (for example, for a CEPS steering system) and/or in the inputshaft (for example, for a DP or BD steering system). The torque sensor260 provides the torque values to the controller 256 for processing,including the determination of an amount of compensating torque that maybe required.

The yaw rate sensor 262 measures a yaw velocity of the vehicle. The yawrate sensor 262 provides the yaw velocity values to the controller 256for processing, including the determination of whether the vehicle istravelling on a straight line path.

The wheel sensors 266 measure a tire angular velocity. The wheel sensors266 provide the wheel angular velocity values to the controller 256 forprocessing, including for determining whether the vehicle is travellingon a straight line path.

The controller 256 is coupled to the compass 250, the GPS device 252,the sensor array 254, and the steering system 150. The controller 256controls various aspects of the steering system 150, includingactivation and de-activation of the compensation torque of the steeringfunctionality, based on the values and information obtained from atleast one of the compass 250, the GPS device 252, and the sensor array254. These features are preferably performed by the controller 256,along with the compass 250, the GPS device 252, the sensor array 254,and the steering system 150 in accordance with the steps of the process300 depicted in FIG. 3 and described further below in connectiontherewith.

The controller 256 also may be in operative communication with an enginecontrol unit of the vehicle corresponding to the vehicle steering system150 via a communications bus (for example, a CAN bus), in order toreceive some of the above-referenced values, and/or additional data(such as vehicle parameters that may include, among others, vehiclespeed, engine Revolutions Per Minute (RPM), and the like), for examplein performing various steps of the process 300 of FIG. 3.

As depicted in FIG. 2, the controller 256 comprises a computer systemthat includes a processor 270, a memory 272, an interface 274, a storagedevice 276, and a bus 278. The processor 270 performs the computationand control functions of the computer system and the controller 256, andmay comprise any type of processor or multiple processors, singleintegrated circuits such as a microprocessor, or any suitable number ofintegrated circuit devices and/or circuit boards working in cooperationto accomplish the functions of a processing unit. During operation, theprocessor 270 executes one or more programs 280 contained within thememory 272 and, as such, controls the general operation of thecontroller 256 and the computer system, preferably in executing thesteps of the processes described herein, such as the process 300depicted in FIG. 3 and described further below in connection therewith.In the depicted embodiment, the controller 256 is the computer system.However, in some embodiments the controller 256 may include one or moreitems in addition to the computer system.

The memory 272 can be any type of suitable memory. This would includethe various types of dynamic random access memory (DRAM) such as SDRAM,the various types of static RAM (SRAM), and the various types ofnon-volatile memory (PROM, EPROM, and flash). The bus 278 serves totransmit programs, data, status and other information or signals betweenthe various components of the computer system. In a preferredembodiment, the memory 272 stores the above-referenced program 280 alongwith one or more stored values 282 for use in controlling the vehiclesteering system 150 and the components and subsystems thereof (includingthe on-center functionality with torque compensation) in accordance withsteps of the process 300 depicted in FIG. 3 and described further belowin connection therewith. In certain examples, the memory 272 is locatedon and/or co-located on the same computer chip as the processor 270.

The interface 274 allows communication to the computer system, forexample from a system driver and/or another computer system, and can beimplemented using any suitable method and apparatus. It can include oneor more network interfaces to communicate with other systems orcomponents. The interface 274 may also include one or more networkinterfaces to communicate with technicians, and/or one or more storageinterfaces to connect to storage apparatuses, such as the storage device276.

The storage device 276 can be any suitable type of storage apparatus,including direct access storage devices such as hard disk drives, flashsystems, floppy disk drives and optical disk drives. In one exemplaryembodiment, the storage device 276 comprises a program product fromwhich memory 272 can receive a program 280 that executes one or moreembodiments of one or more processes of the present disclosure, such asthe process 300 of FIG. 3 or portions thereof. In another exemplaryembodiment, the program product may be directly stored in and/orotherwise accessed by the memory 272 and/or a disk (e.g. disk 284), suchas that referenced below.

The bus 278 can be any suitable physical or logical means of connectingcomputer systems and components. This includes, but is not limited to,direct hard-wired connections, fiber optics, infrared and wireless bustechnologies. During operation, the program 280 is stored in the memory272 and executed by the processor 270.

It will be appreciated that while this exemplary embodiment is describedin the context of a fully functioning computer system, those skilled inthe art will recognize that the mechanisms of the present disclosure arecapable of being distributed as a program product with one or more typesof non-transitory computer-readable signal bearing media used to storethe program and the instructions thereof and carry out the distributionthereof, such as a non-transitory computer readable medium bearing theprogram and containing computer instructions stored therein for causinga computer processor (such as the processor 270) to perform and executethe program. Such a program product may take a variety of forms, andthat the present disclosure applies equally regardless of the particulartype of computer-readable signal bearing media used to carry out thedistribution. Examples of signal bearing media include: recordable mediasuch as floppy disks, hard drives, memory cards and optical disks, andtransmission media such as digital and analog communication links. Itwill similarly be appreciated that the computer system may alsootherwise differ from the embodiment depicted in FIG. 2, for example inthat the computer system may be coupled to or may otherwise utilize oneor more remote computer systems and/or other control systems.

FIG. 3 is a flowchart of a process 300 for implementation of thesupplemental controls of the steering system for a vehicle, inaccordance with an exemplary embodiment. The process 300 can be utilizedin connection with the vehicle 100 of FIG. 1 and the steering system 150and control system 170 of FIGS. 1 and 2, in accordance with an exemplaryembodiment.

As depicted in FIG. 3, the process 300 begins with the step of measuringa torque applied by the driver against the steering system 150 of FIGS.1 and 2 (step 302). In one embodiment, the torque is measured by atorque sensor 260 of FIG. 2 as a measure of the torque applied by thedriver against the steering wheel 212 of FIG. 2. In another embodiment,the torque is measured by a torque sensor 260 of FIG. 2 as a measure ofthe torque against the steering column assembly 214 of FIG. 2 as aresult of the driver's engagement of the steering wheel 212. Torquevalues are preferably measured at various points in time, mostpreferably continuously, throughout the process 300.

A determination is made as to whether a relatively long-term torquecompensation is required (step 304). The determination of step 304 ismade based on the torque of various iterations of step 302 over time.Specifically, if the amount of torque applied to the steering wheel isgreater than a predetermined torque threshold for at least apredetermined amount of time, then a relatively long-term torquecompensation would be required for the functionality of the steeringsystem (for example to correct for an alignment or tire issue with thevehicle). The long-term torque compensation of step 304 is preferablyperformed across multiple ignition cycles.

If it is determined in step 304 that long-term torque compensation isrequired, then a long-term compensating torque is calculated (step 306).The compensating torque comprises an amount of torque required tocounteract any alignment or other issues with the vehicle that requiresustained driver effort on a straight line roadway. The compensatingtorque is preferably calculated by the processor 270 of FIG. 2 using anintegral control action.

The compensating torque is then provided to the steering system (step307). Specifically, during step 307, compensating torque is provided tothe steering system in the amount calculated in step 306. Preferably,the compensating torque is provided based on instructions provided bythe processor 270 of FIG. 2 to the motor 219 of FIG. 2 to providecompensating torque against the rack 216 of FIG. 2. In certainembodiments, the compensating torque may be provided based oninstructions provided by the processor 270 of FIG. 2 to the motor 219 ofFIG. 2 to provide compensating torque against the steering columnassembly 214 and/or the steering wheel 212 of FIG. 2. The process thenproceeds to step 310, described further below.

Conversely, if it is determined in step 304 that long-term torquecompensation is not required, then no long-term torque compensation isprovided (step 308). The sub-process of steps 304-308 are preferablyperformed at various points in time, most preferably continuously,throughout the process 300.

During step 310, a compass heading is measured. The compass heading ispreferably measured by the compass 250 of FIG. 2, and the compassheading values are provided to the processor 270 of FIG. 2 forprocessing. Compass heading values are preferably measured at variouspoints in time, most preferably continuously, throughout the process300.

A change in the compass heading value is calculated (step 312). Thechange in compass heading values is preferably calculated by theprocessor 270 of FIG. 2 based on compass heading values from differentiterations of step 310 during a current ignition cycle. In one exemplaryembodiment, a threshold of approximately two degrees heading change maybe utilized for certain vehicles. However, this may vary in differentembodiments, and the applicable thresholds may be different for eachvehicle. The change in compass heading is preferably calculated atvarious points in time, most preferably continuously, throughout theprocess 300.

A GPS heading is also obtained (step 314). The GPS heading is preferablyreceived or determined by the GPS device 252 of FIG. 2, and the GPSheading values are provided to the processor 270 of FIG. 2 forprocessing. GPS heading values are preferably measured at various pointsin time, most preferably continuously, throughout the process 300.

A change in GPS heading values is calculated (step 316). The change inGPS heading values is preferably calculated by the processor 270 of FIG.2 based on GPS heading values from different iterations of step 316during a current ignition cycle. In one exemplary embodiment, athreshold of approximately two degrees heading change may be utilizedfor certain vehicles. However, this may vary in different embodiments,and the applicable thresholds may be different for each vehicle. Thechange in GPS heading is preferably calculated at various points intime, most preferably continuously, throughout the process 300.

A yaw velocity of the vehicle is also measured (step 318). The yawvelocity is preferably measured by the yaw sensor 262 of FIG. 2, and theyaw velocity values are provided to the processor 270 of FIG. 2 forprocessing. Yaw velocity values are preferably measured at variouspoints in time, most preferably continuously, throughout the process300.

A tire angular velocity is measured (step 326). The tire angularvelocity is preferably measured by the wheel speed sensors 266 of FIG.2, and the tire angular velocity values are provided to the processor270 of FIG. 2 for processing. Tire angular velocity values arepreferably measured at various points in time, most preferablycontinuously, throughout the process 300. Also as part of step 326, adifference is calculated as to the tire angular velocities of tires thatare side-by-side one another on the vehicle.

A determination is made as to whether the vehicle is travelling on astraight line path (or roadway) (step 328). Step 328 preferablycomprises a determination as to whether the vehicle is driving on arelatively straight roadway, as compared with a relatively short radiusturn (such as at a traffic light) or a relatively long radius turn (suchas at a freeway ramp). The determination of step 328 is preferably madeby the processor 270 of FIG. 2 based on one or more of the values ofsteps 310-326.

In one embodiment of step 328, the vehicle is determined to betravelling on a straight-line path if the change in compass heading ofstep 312 is less than a predetermined threshold. In one such exemplaryembodiment, a threshold of approximately two degrees heading change maybe utilized for certain vehicles. However, this may vary in differentembodiments, and the applicable thresholds may be different for eachvehicle.

In another embodiment of step 328, the vehicle is determined to betravelling on a straight-line path if the change in GPS heading of step316 is less than a predetermined threshold. In one such exemplaryembodiment, a threshold of approximately two degrees heading change maybe utilized for certain vehicles. However, this may vary in differentembodiments, and the applicable thresholds may be different for eachvehicle.

In another embodiment of step 328, the vehicle is determined to betravelling on a straight-line path if the yaw velocity of step 318 isless than a predetermined threshold. In one such exemplary embodiment, athreshold of approximately one half degrees per second (0.5 deg/sec) maybe utilized for certain vehicles. However, this may vary in differentembodiments, and the applicable thresholds may be different for eachvehicle.

In another embodiment of step 328, the vehicle is determined to betravelling on a straight-line path if a difference in tire angularvelocities of step 326 (namely, of wheels that are side-to-side of oneanother) is less than a predetermined threshold. In one such exemplaryembodiment, a threshold of approximately one tenth of one percent (0.1%)may be utilized for certain vehicles. However, this may vary indifferent embodiments, and the applicable thresholds may be differentfor each vehicle. In one embodiment, the difference of the angularvelocities must be below the percentage of the angular velocity ofeither tire for the determination to be made that the vehicle istravelling on a straight-line path.

If it is determined in step 328 that the vehicle is travelling on astraight line path, then a velocity of the vehicle is calculated (step330). In one embodiment, the vehicle velocity is calculated by theprocessor 270 of FIG. 2 based on a wheel speed of the vehicle asmeasured by the wheel speed sensors 266 of FIG. 2. In certainembodiments, the vehicle velocity may be received by the processor 270as a signal communicated along a communication link (e.g. a CAN bus)and/or may be calculated by processor 270 from data received along sucha communication link (such as, by way of example, transmission outputspeed sensor data).

A determination is made as to whether the vehicle velocity of step 330is greater than a predetermined threshold (step 332). In one suchexemplary embodiment, a threshold of approximately thirty miles per hour(30 mph) may be utilized for certain vehicles. However, this may vary indifferent embodiments, and the applicable thresholds may be differentfor each vehicle. This determination is preferably made by the processor270 of FIG. 2.

If the conditions of steps 328 and 332 are both satisfied (namely, thatthe vehicle velocity is travelling along a straight line path asdetermined in step 328 and that the vehicle velocity is greater than thethreshold of step 332), then it is determined that a passive or learningcompensatory state exists (step 336). Other conditions may also beconsidered for determination of this valid compensatory state, such asvehicle acceleration (braking or driving) and can likewise be includedas additional criteria for determination of state. This determination ispreferably made by the processor 270 of FIG. 2.

Conversely, if at least one of the conditions of steps 328 or 332 arenot satisfied (namely, that the vehicle is not travelling on a straightline path or roadway, as determined in step 328, or that the velocity isless than or equal to the threshold of step 332), then it is determinedthat compensatory state conditions do not presently exist (step 338).This determination is also preferably made by the processor 270 of FIG.2.

If it is determined in step 336 that compensatory state conditionsexist, then learning is provided for the long-term torque compensationfor the compensated steering functionality (step 340). Specifically, thetorque values of step 302 during time periods corresponding to thecompensatory state conditions of step 336 are stored in the memory 272of FIG. 2 as stored values 282 therein for use in updating that amountof relatively long-torque compensation calculated in step 306,preferably based on an integral or equivalent control action. Thislearning provides adjustment or updating of the relatively long-termtorque compensating values of step 306 to include current, compensatorystate conditions in addition to the previous compensatory stateconditions that would have already been reflected in step 306. In oneembodiment, the learning/adjustment of step 340 is performed acrossmultiple ignition cycles for the vehicle. The learning/adjustment ofstep 340 is preferably performed by the processor 270 of FIG. 2, andresulting updated values are preferably stored in the memory 280 of FIG.2 as stored values 282 therein.

In addition, a determination is made as to whether short term torquecompensation is required (step 342). Short-term compensation may berequired if a short term disturbance may result in a lead/pull conditionof the vehicle. A lead/pull condition refers to a condition of thevehicle wherein the vehicle regularly leads or pulls in a direction thatis not intended by the driver. For example, a lead/pull condition wouldrequire the driver to apply torque even if the vehicle were travellingalong a straight line path. Short-term compensation may be required, forexample, due to wind gusts or slopes in the road (for example, in banksor crowns in the road). The determination of whether short termcompensation required is similar to the determination of step 304,except that the determination applies within a shorter time frame (andwithin a current ignition cycle). Specifically, if the amount of torqueapplied to the steering wheel is greater than a predetermined torquethreshold for at least a predetermined amount of time (namely, arelatively shorter amount of time as compared with the determination ofstep 304) within a current ignition cycle, then a relatively short-termtorque compensation would be required for the functionality of thesteering system (for example to adjust for wind gusts, road banks,and/or other temporary conditions). In one embodiment, thisdetermination is made by the processor 270 of FIG. 2 using the level oftorque applied to the steering wheel 212 of FIG. 2 (for example,measured by the torque sensors 260 of FIG. 2).

If it is determined that short term torque compensation is required,then short-term torque compensation is provided (step 344).Specifically, during step 344, compensating torque is provided for thesteering system in an amount that is calculated to offset the short-termdisturbance (for example, the wind gust or the bank or the crown in theroad). In certain embodiments, the short-term torque compensation isdisabled if the braking system 160 of FIG. 1 is engaged by the driver ofthe vehicle 100. Preferably, the compensating torque is provided basedon instructions provided by the processor 270 of FIG. 2 to the motor 219of FIG. 2 to provide compensating torque against the rack 216 of FIG. 2.In certain embodiments, the compensating torque may be provided based oninstructions provided by the processor 270 of FIG. 2 to the motor 219 ofFIG. 2 to provide compensating torque against the steering columnassembly 214 or the steering wheel 212 of FIG. 2. Conversely, if it isdetermined in step 342 that short term compensation is not required,then no short-term torque compensation is provided (step 346).

Returning to step 338, if it is determined that the vehicle is not in acompensatory state condition for the compensating steeringfunctionality, then no learning or adjustment of the long term torquecompensation of step 306 is provided (specifically, step 340 is notperformed) (step 348). In addition, no short-term compensating torque isprovided (specifically, step 344 is not performed) (step 350).Accordingly, in one embodiment, the long term torque compensationlearning of step 340 and the providing of short-term torque compensationof step 344 are not provided when it is determined in step 328 that thevehicle is not travelling on a straight line path. In one suchembodiment, torque compensation is completely terminated by theprocessor when the vehicle is not travelling on a straight line path. Inanother embodiment, when the vehicle is not travelling on a straightline path, a level of lead/pull compensation torque may be maintained bythe processor based on previous learning (i.e. from before the currentcondition in which the vehicle is not traveling along a straight linepath). In addition, the long term torque compensation of step 340 andthe providing of short-term torque compensation of step 344 are also notprovided if the vehicle velocity is less than or equal to the thresholdof step 332.

Thus, certain features of the compensation functionality (namely, thelong term torque compensation learning and the providing of the shortterm torque compensation) are disabled when the vehicle is nottravelling on a straight line path. This allows for potentially moreaccurate and desirable results, for example because a vehicle turn(including a relatively large-radius turn, such as for a freeway ramp)will not be interpreted as requiring torque compensation (because thetorque is desired by the driver to execute the turn, and is not due toan alignment issue, a wind gust, a road bank or crown, and/or some otherissue requiring compensation). In contrast, previous techniques may nothave been able to distinguish such turns (particularly, such relativelylarge-radius turns) from straight line vehicle operation. Thesub-processes of steps 328-350 are preferably performed at variouspoints in time, most preferably continuously, throughout the process300.

It will be appreciated that the disclosed methods and systems may varyfrom those depicted in the Figures and described herein. For example, asmentioned above, the vehicle 100 of FIG. 1, the steering system 150 andthe computer system 170 of FIGS. 1 and 2, and/or portions and/orcomponents thereof may vary, and/or may be disposed in whole or in partin any one or more of a number of different vehicle units, devices,and/or systems, in certain embodiments. In addition, it will beappreciated that certain steps of the process 300 may vary from thosedepicted in FIG. 3 and/or described above in connection therewith. Itwill similarly be appreciated that certain steps of the process 300 mayoccur simultaneously or in a different order than that depicted in FIG.3 and/or described above in connection therewith.

Accordingly, methods and systems are provided for controlling steeringsystems for vehicles. The disclosed methods and systems provide forpotentially improved use of steering systems, for example bydifferentiating between straight-line travel as compared with vehicleturns, including relatively large-radius turns such as freeway ramps. Incertain embodiments, the application of a short-term offset torque (forexample, in the case of a wind gust or a crown in the road) may bedisabled when the vehicle is in a turn, and/or long-term learning of anoffset torque (for example, to compensate for alignment imbalancesand/or other vehicle issues) may be disabled when the vehicle is in aturn.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the exemplary embodiment or exemplary embodiments. Itshould be understood that various changes can be made in the functionand arrangement of elements without departing from the scope of theinvention as set forth in the appended claims and the legal equivalentsthereof.

What is claimed is:
 1. A method of controlling a steering system of avehicle, the method comprising: determining whether the vehicle is on astraight line path based on one or more of the following values: acompass heading, a global positioning system (GPS) heading, a yawvelocity, and a difference in tire angular velocities; and selectivelyimplementing a lead or pull feature of the steering system based onwhether it is determined that the vehicle is on a straight line path,wherein the step of selectively implementing the lead or pull feature ofthe steering system comprises: providing a first level of lead/pullcompensation based on current conditions when the vehicle is on astraight line path; and maintaining a second level of lead/pullcompensation torque, different from the first level, based on previouslearning from prior to the current conditions, when the vehicle is noton a straight line path.
 2. The method of claim 1, further comprising:measuring a torque provided by a driver of the vehicle to a steeringcolumn of the vehicle, wherein the step of selectively implementing thelead or pull feature of the steering system comprises: using the torquefor calculating a compensating steering torque for the lead or pullfeature when the vehicle is on a straight line path; and not using thetorque for calculating the compensating steering torque for the lead orpull feature when the vehicle is not on a straight line path.
 3. Themethod of claim 1, wherein the step of determining whether the vehicleis on a straight line path comprises: obtaining a first compass headingvalue at a first time; obtaining a second compass heading value at asecond time; and determining that the vehicle is on a straight line pathif a difference between the first and second compass heading values isless than a predetermined threshold.
 4. The method of claim 1, whereinthe step of determining whether the vehicle is on a straight line pathcomprises: obtaining a first GPS heading value at a first time;obtaining a second GPS heading value at a second time; and determiningthat the vehicle is on a straight line path if a difference between thefirst and second GPS heading values is less than a predeterminedthreshold.
 5. The method of claim 1, wherein the step of determiningwhether the vehicle is on a straight line path comprises: determiningthat the vehicle is on a straight line path if the yaw velocity is lessthan a predetermined threshold.
 6. The method of claim 1, wherein thestep of determining whether the vehicle is on a straight line pathcomprises: determining that the vehicle is on a straight line path ifthe difference in tire angular velocities is less than a predeterminedthreshold.
 7. A system for controlling the steering system of a vehicle,the system comprising: a detection unit configured to obtain one or moreof the following values: a compass heading, a global positioning system(GPS) heading, a yaw velocity, and a tire angular velocity; and aprocessor coupled to the detection unit and configured to: determinewhether the vehicle is on a straight line path using one or more of thecompass heading, the GPS heading, the yaw velocity, and the tire angularvelocities; and selectively implement a lead or pull feature of thesteering system based on whether it is determined that the vehicle is ona straight line path, wherein the processor is configured to: provide afirst level of lead/pull compensation based on current conditions whenthe vehicle is on a straight line path; and maintain a second level oflead/pull compensation torque, different from the first level, based onprevious learning from prior to the current conditions, when the vehicleis not on a straight line path.
 8. The system of claim 7, wherein: thedetection unit comprises a compass configured to provide: a firstcompass heading value at a first time; and a second compass headingvalue at a second time; and the processor is configured to determinethat the vehicle is on a straight line path if a difference between thefirst and second compass heading values is less than a predeterminedthreshold.
 9. The system of claim 7, wherein: the detection unitcomprises a GPS system component configured to provide: a first GPSheading value at a first time; and a second GPS heading value at asecond time; and the processor is configured to determine that thevehicle is on a straight line path if a difference between the first andsecond GPS heading values is less than a predetermined threshold. 10.The system of claim 7, wherein: the detection unit comprises a sensorconfigured to measure the yaw velocity; and the processor is configuredto determine that the vehicle is on a straight line path if the yawvelocity is less than a predetermined threshold.
 11. The system of claim7, wherein: the detection unit comprises a sensor configured to measurethe tire angular velocities; and the processor is configured todetermine that the vehicle is on a straight line path if the tireangular velocity difference is less than a predetermined threshold. 12.A vehicle comprising: a drive system; an electric power steering systemcoupled to the drive system; and a control system coupled to theelectric power steering system, the control system comprising: adetection unit configured to obtain one or more of the following values:a compass heading, a global positioning system (GPS) heading, a yawvelocity, and tire angular velocities; and a processor coupled to thedetection unit and configured to: determine whether the vehicle is on astraight line path using one or more of the compass heading, the GPSheading, the yaw velocity, and the tire angular velocities; activate alead/pull compensation feature of the electric power steering system ifit is determined that the vehicle is on a straight line path; andterminate the lead/pull compensation or maintain a level of lead/pullcompensation torque based on previous learning if it is determined thatthe vehicle is not on a straight line path, wherein the processor isconfigured to: provide a first level of lead/pull compensation based oncurrent conditions when the vehicle is on a straight line path; andmaintain a second level of lead/pull compensation torque, different fromthe first level, based on previous learning from prior to the currentconditions, when the vehicle is not on a straight line path.
 13. Themethod of claim 1, wherein the step of selectively implementing the leador pull feature of the steering system comprises: activating lead/pullcompensation when the vehicle is on a straight line path; andde-activating the lead/pull compensation when the vehicle is not on astraight line path.
 14. The method of claim 1, further comprising:measuring a torque value provided against the steering system; measuringa velocity of the vehicle; and selectively utilizing the torque valuefor updating long-term torque compensation values for the lead or pullfeature for learning and subsequent use in connection with the lead/pullfeature in the future, based on (i) whether the vehicle is on a straightline path and (ii) the velocity of the vehicle.
 15. The method of claim14, wherein the step of selectively utilizing the torque valuecomprises: storing the torque value for use in updating the long-termtorque compensation values for the lead or pull feature for learning andsubsequent use in connection with the lead/pull feature in the future,provided that both of the following are satisfied, namely: (a) thevehicle is on a straight line path and (b) the velocity of the vehicleexceeds a predetermined threshold; and not storing the torque value foruse in updating the long-term torque compensation values for the lead orpull feature for learning and subsequent use in connection with thelead/pull feature in the future, if either of the following aresatisfied, namely: (c) the vehicle is not on a straight line path or (d)the velocity of the vehicle does not exceed the predetermined threshold,or both.
 16. The system of claim 7, wherein the processor is configuredto: activate lead/pull compensation when the vehicle is on a straightline path; and de-activate the lead/pull compensation when the vehicleis not on a straight line path.
 17. The system of claim 7, wherein: thedetection unit is configured to: measure a torque value provided againstthe steering system; and measure a velocity of the vehicle; and theprocessor is configured to selectively utilize the torque value forupdating long-term torque compensation values for the lead or pullfeature for learning and subsequent use in connection with the lead/pullfeature in the future, based on (i) whether the vehicle is on a straightline path and (ii) the velocity of the vehicle.
 18. The vehicle of claim12, wherein: the detection unit is configured to: measure a torque valueprovided against the steering system; and measure a velocity of thevehicle; and the processor is configured to selectively utilize thetorque value for updating long-term torque compensation values for thelead/pull feature for learning and subsequent use in connection with thelead/pull compensation feature in the future, based on (i) whether thevehicle is on a straight line path and (ii) the velocity of the vehicle.